Grease composition



United States Patent 3,100,193 GREASE COMPOSITION Reuben A. Swenson and Stephen J. Zajac, Whiting, Ind.,

assignors to Standard ()il Company, Chicago, 11]., a corporation of Indiana No Drawing. Filed Aug. 24, 1960, Ser. No. 51,508 4 Claims. (Cl. 25240.5)

This invention relates to lubricant greases, and more particularly concerns a novel grease of the calcium acetate complex type which is characterized by improved age hardening characteristics.

Lime soap greases containing a complex of calcium soaps of both a long chain fatty acid and a short chain fatty acid such as acetic acid have long been employed for moderate temperature duty. However, a major difficulty with such greases is that they tend to harden upon aging. This not only adversely affects their performance but is physically unattractive from the standpoint of the consumer. Accordingly, a primary object of the present invention is to provide a lime soap complex grease characterized by outstanding resistance to age hardening.

It has now been discovered that age hardening of lime soap complex greases may be inhibited by incorporating therein a small amount, normally less than 1% by weight, of an acetoxy substituted long chain fatty acid. In addition, the inventive acetoxy fatty acid greatly improves the grease yield, that is, it materially lowers the amount of soap required to produce a grease of a given ASTM penetration.

Lime soap complex greases, as indicated earlier, comprise a lubricant oil base or vehicle thickened to grease consistency with calcium soaps of both a long chain and a short chain fatty acid. The long chain soaps ordinarily are present in a concentration of about 120% by weight, while the short chain soap may be present in about 110% by weight.

Long chain fatty acids which are used in preparing lime soap complex greases are made from fatty acids which advantageously contain from about to about 30 carbon atoms per molecule, optimally from about 12 to about 24 carbon atoms. Such fatty acids may "be derived from natural sources, e.g. from mineral fats or vegetable oils, and may be saturated, unsaturated, hydroxy, or hydroxyunsaturated. Examples of individual fatty acids, which are present in varying amounts in natural materials, include: the saturated acids such as lanric, myn'stic, palmitic, stearic, arachidic, and lbehenic acids; the unsaturated acids such as lauroleic, myristoleic, palmitoleic, and oleic acids; the hydroxy acids such as 12-hydroxy stearic and 9,10-dihydroxy stearic acids; and the hydroxyunsaturated acids typified by ricinoleic (12-hydroxy-9- octadecanoic acid). Unsaturated acids may be completely or partially hydrogenated to remove such unsaturation before being employed in the manufacture of lime base greases. Where fatty acids are derived from natural sources, the resultant acid will ordinarily be a mixture of several fatty acids and may be employed either in this condition or after suitable distillation to recover a single fatty acid.

Short chain fatty acids which are present in lime soap complex greases are prepared from fatty acids having not more than 6 carbon atoms per molecule. Calcium acetate is the short chain soap most commonly employed, although soaps from formic, n-butyric, isobutyric, and n-valeric acids, may also be employed.

The lubricant vehicles or bases which comprise the major amount of greases and oleaginous normally liquid lubricants which can be mineral lubricating oils, silicone polymer oils, synthetic hydrocarbon lubricating oils, synthetic lubricating oils of various types such as poly-alkylene glycols and their derivatives, high molecular weight ice esters of dicarboxylic acids, polyfiuoro derivatives of organic compounds such as the trifluorovinyl chloride polymers known as Fluorol ube and the trifluorochloroethylene polymers known as Kel-F, etc.

Mineral lubricating oils normally are the most commonly employed lubricant vehicles in preparing lime soap complex greases. These oils are in the lubricating oil viscosity range, e.g. from about 50 SSU at F. to about 300 SSU at 210 F. Mineral oils are preferably solvent extracted to substantially remove low viscosity index constituents, e.g. aromatics, with known selective solvents such as phenol, Chlorex, liquid sulfur dioxide, etc.

The inventive age hardening inhibitor is an acetoxy substituted long chain fatty acid. This material is ordinarily present at a concentration within the range of about 0.1 to about 3% by weight in the finished grease, optimally at a concentration Within the range of about 0.1 to about 1.0 weight percent. Any of the acetoxy substituted long chain fatty acids are suitable, particularly those having from 10 to about 30, more desirably from 12 to about 24, carbon atoms in the fatty acid chain. At present (1960) only the 12-acetoxy stearate is available commercially, although acetoxy derivatives of hydroxy fatty acids, such as ricinoleic acid, 9,10-dihydroxy stearic acid (with either one or both of the hydroxy groups substituted with an acetoxy radical), and lO-hydroxy stearic acid may be prepared. It is conceivable, however, that other acetoxy substituted fatty acids, particularly the acetoxy substituted saturated fatty acids may also be available and accordingly are Within the scope of this invention. While the acetoxy substituted long chain fatty acid may be employed in either free or combined form, in order to afford more desirable solubility properties it is preferred that the acetoxy substituted fatty acid additive be employed as an ester, typically the triglyceride or the methyl or ethyl ester.

Lime soap greases containing acetoxy substituted long chain fatty acids may be prepared in a manner similar to that employed in conventional lime soap complex grease manufacture. Generally, the lime soap is prepared in situ by saponification of the long chain fatty acid and the short chain fatty acid While in solution in all or part of the lubricating fluid which is to be the major constituent of the final grease. Calcium oxide or hydroxide for saponification is added to the solution as a dry oil slurry or as an aqueous solution. The mixture of soap and oil is heated to effect dehydration with stirring, and the balance of the oil is then added either hot or col-d, depending upon the desired heat treatment for optimum grease fiber growth. During the admixture of additional oil the system may be rehydrated to the desired extent by adding liquid Water. The grease is ordinarily finished by cooling and milling in a colloid mill or in a homogenizer.

The acetoxy substituted long chain fatty acid may be added at any stage of grease manufacture. It is advantageous, however, to introduce this before commencement of saponification. At the same time, other additives, for example oxidation and corrosion inhibitors, may be introduced.

To exemplify the preferred practice of the present invention the following example is presented. It will be understood that this example is for illustrative purposes only and is not to be considered wholly definitive with respect to scope or conditions.

Example In this example a mineral oil base grease thickened with a lime soap complex and inhibited with acetoxy stearate was prepared.

The acetoxy stearate is a hydrogenated triglyceride of acetyl ricinoleate and is manufactured by the Baker Castor Oil Company and sold as Para-cin 8.

To a steam or electrically heated grease kettle were added 1.4 lbs. of solvent extracted mineral oil, 0.64 lb. of hydrated lime, and the mixture stirred to a smooth slurry for45 minutes. Then 2.6 lbs. of oil, 0.8 lb. of glacial acetic'acid, and 0.8 lb. of Emery F-996-S fatty acids were added. The Emery fatty acids comprise a mixture of 16 and '18 carbon atoms saturated mono'carboxylic acids. At the same time an oxidation and corrosion inhibitor described below was also added in the amount of 100 g. Y The resultant mixture was then heated from an initial 140 F. to 278 F. over a period of about 1 hour. About 50 g. of water was added and the temperature was then increased to 283 F. 4 lbs. of additional oil was introduced, and after the temperature reached 303 F. an additional '5 g. of water was added. When the temperature reached 467 F. heating was discontinued and the balance of oil and inhibitors was added. The mixture was permitted to cool to room temperature and then reheated to 230 F. and milled.

The resultant grease, designated as grease A had the composition and properties described below. A similar grease, identified as grease B prepared in the same way but containing more than twice as much soap but no acetoxy stearate was similarly prepared, and its composition and properties are also indicated below.

Grease Grease "A" B7 1 Acetoxy stearate, weight percent 0. 76 Nil Emery F-QQEi-S fatty acids, weight percent 2. 74 6. 2 Glacial acetic acid, weight percent 2. 74 6. 2 Hydrated lime, weight percent 2. 3 4. 8 Oxidation and corrosion inhibitors, 1 weight percent 0.52 1. 16 Solvent extracted SAE-40 mineral oil, weight percent 92. 12 84. Calcium soap, weight percent 6. 6 14. 8

Penetration, ASTM Method 217-52'1 As made (unworked/Worked) 314/313 317/318 After 2 months (unworkedlworked) 310/315 211/304 After 3 months (unworked/w orked) 189/291 After 1 year (unworkcdlworked) 300/353 1 Predominately Cu and C15 saturated monocarbcxylic acids, having an iodine value (Wijs) of about 2.0, a free fatty acid content (as oleic) of about 98.0%, a total fatty acid content (as oleic) of about 104.5%, and containing less than 1.0% unsaponifiables.

2 parts by weight Ortholeum 300 (Du Pont inhibitor), 10 parts phenothiazine, 10 parts dilauryl selem'de, and 22 parts sorbitan monooleute It will be evident from a comparison of grease A with [grease B that the former, containing acetoxy stearate, had the same ASTM penetrations, even though the former contained less than half the lime (calcium) soap content.

Moreover, as the table above indicates, acetoxy stearate substantially completely inhibited age hardening; the uninhibited grease B aged 128 points hard in only 3 months, whereas the inhibited grease A aged only 14 points soft in 1 year.

Thus it is apparent that we have provided an outstanding lime soap complex grease which is unusually resistant to age hardening and which materially improves grease yield. While the invention has been described with particularreference to an example thereof it will be evident that thisis by way of illustration only. Accordingly it is contemplated that alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description, and it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

We claim:

1.'A lime soap lubricant grease composition comprising a mineral oil lubricant base, from about one to about twenty percent by weight of a calcium soap of a long chain fatty acid, from about one to about ten percent by weight of a calcium soap of a short chain fatty acid, and a small amount, effective to inhibit age hardening, of a member selected from the group consisting of an acetoxy substituted long chain fatty acid. having from ten to about thirty carbon atoms in the fatty acid chain in free acid form, and triglycerides, methyl and ethyl esters of such acetoxy substituted long chain fatty acids.

2. The grease composition of claim 1 wherein said small amount is from about 0.1 to about 1.0 percent by weight.

3. The grease composition of claim 1 wherein said member is the triglyceride of acetoxy stearate.

4. A lime soap lubricant grease composition comprising a mineral oil base, from about 1 to about 20 percent by weight of a calcium soap of a long chain fatty acid having from about 12 to about 24 carbon atoms per molecule, from about 1 to about 10 percent by weight of a calcium soap of acetic acid, and from about 0.1 to about 1.0 percent by weight of the triglyceride of acetoxy stearate.

References Cited in the file of this patent UNITED STATES PATENTS 2,589,973 Smith et a1 Mar. 18, 1952 2,712,527 Mikeska a a1. July s, 1955 2,719,124 Mikeska et al Sept. 27, 1955 

1. A LIME SOAP LUBRICANT GREASE COMPOSITION COMPRISING A MINERAL OIL LUBRICANT BASE, FROM ABOUT ONE TO ABOUT TWENTY PERCENT BY WEIGHT OF A CALCIUM SOAP OF A LONG CHAIN FATTY ACID, FROM ABOUT ONE TO ABOUT TEN PERCENT BY WEIGHT OF A CALCIUM SOAP OF A SHORT CHAIN FATTY ACID, AND A SMALL AMOUNT, EFFECTIVE TO INHIBIT AGE HARDENING, OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF AN ACETOXY SUBSTITUTED LONG CHAIN FATTY ACID, HAVING FROM TEN TO ABOUT THIRTY CARBON ATOMS IN THE FATTY ACID CHAIN IN FREE ACID FROM, AND TRIGLYCERIDES, METHYL AND ETHYL ESTERS OF SUCH ACETOXY SUBSTITUTED LONG CHAIN FATTY ACIDS. 